1. Field of the Invention
The present invention relates to a control device and method for a vehicle.
2. Description of Related Art
Vehicles using a carburetor, which is a mechanical vaporizing device, are known. In a vehicle using a carburetor, depending on the combustion state of an engine, a catalyst provided in an exhaust gas passage may be burned or suffer degradation. More specifically, when the ignition is cut, for example, when the engine over-revs and the engine speed exceeds an allowable maximum rotation speed, or when the engine is turned off, unburned fuel may flow into the exhaust gas passage. Unburned fuel that flows into the exhaust gas passage may self-ignite and cause the catalyst to be burned or suffer thermal degradation. Further, the unburned fuel and the catalyst will react, resulting in poorer catalyst performance.
In light of these problems, Japanese Patent No. 2860084 discloses a solenoid opening/closing valve that is provided in a fuel passage of a carburetor. When an abnormality occurs in the combustion state of the engine, the solenoid opening/closing valve is controlled to limit the supply of fuel to the engine.
Fuel such as gasoline includes impurities such as gummy residue. Therefore, when the engine is stopped for a long time, the solenoid opening/closing valve may stick or have difficulty in moving smoothly due to the impurities in the fuel.
Accordingly, an initial operation of the solenoid opening/closing valve is preferably performed when the vehicle is activated to confirm that the solenoid opening/closing valve is operating smoothly. More specifically, when the vehicle is activated, the solenoid opening/closing valve is preferably driven one or more times. A rider can hear the driving sound of the solenoid opening/closing valve, and can determine whether or not an abnormality of the solenoid opening/closing valve has occurred. In addition, causing the solenoid opening/closing valve to perform the initial operation makes it possible to ensure smooth operation of the solenoid opening/closing valve even if it was not operating smoothly beforehand.
However, when the battery voltage of the vehicle is lower than the drive voltage of the solenoid opening/closing valve, the initial operation of the solenoid opening/closing valve cannot be performed. For example, in a vehicle in which the engine is started by electric power using a starter or the like, the drive voltage of the solenoid opening/closing valve is normally lower than the drive voltage of the starter. Therefore, when the engine is started, it is unlikely that the initial operation of the solenoid opening/closing valve will be performed. In addition, when the rider uses a kick starter or pushes the vehicle to forcibly run it, the engine is forcibly rotated and thereby started. In such a case, the engine is started even if the battery voltage of the vehicle is lower than the drive voltage of the solenoid opening/closing valve. In such a case when the rider starts the engine manually without using a starter or the like, the initial operation of the solenoid opening/closing valve may not be performed.
In addition, when the solenoid opening/closing valve is driven, the fuel supply to the engine is temporarily stopped. Accordingly, the initial operation of the solenoid opening/closing valve is preferably not performed when the engine speed is relatively high. Therefore, the initial operation is preferably not performed in a case where the engine is started at the same time as when the vehicle is activated, and thereafter the engine speed immediately increases. This is because, if the initial operation of the solenoid opening/closing valve is performed, for example, when the vehicle is accelerated from standstill by opening the throttle at the same time as when the vehicle is activated, the engine speed may not increase smoothly in accordance with an increase in throttle opening degree.
In light of the above, the initial operation may not be performed if the engine speed is higher than a determined rotation speed when the vehicle is activated.
If the initial operation of the solenoid opening/closing valve is not performed, the rider cannot easily notice the occurrence of an abnormality, such as sticking of the solenoid opening/closing valve. Accordingly, the rider may run the vehicle in spite of such abnormality, and the solenoid opening/closing valve may not operate properly when fuel to the engine is to be cut.
This problem does not uniquely occur when a solenoid opening/closing valve is used. Rather, it generally occurs when any electronically controlled opening/closing valve that is driven by electric power is used.